Abstract

We experimentally demonstrate plasmonic lenses working in the visible range with well controlled focal lengths using nano-slits in an aluminum film. The fabricated lenses were characterized using confocal scanning optical microscopy. Two lenses with a design focal length 3 µm and 6 µm at 633 nm were investigated in detail. The full-width half-maximum beam width at the focal point was found to be 470 nm and 490 nm, and the extension of the light spot was 1.3 μm and 2.3 μm respectively. Lens performance compared extremely well with the expected behaviour from finite-difference time-domain modeling. The focal length from experiment and simulation agreed to within 3.5%. The lens manufacture was found to be insensitive to deviations from the optimum process parameters indicating that lens components can be reliably designed and produced.

© 2010 OSA

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  1. T. W. Ebbesen, H. J. Lezec, H. F. Ghaemi, T. Thio, and P. A. Wolff, “Extraordinary optical transmission through sub-wavelength holes arrays,” Nature 391(6668), 667–669 (1998).
    [CrossRef]
  2. H. J. Lezec, A. Degiron, E. Devaux, R. A. Linke, L. Martin-Moreno, F. J. Garcia-Vidal, and T. W. Ebbesen, “Beaming light from a subwavelength aperture,” Science 297(5582), 820–822 (2002).
    [CrossRef] [PubMed]
  3. Z. Sun and H. Kim, “Refractive transmission of light and beam shaping with metallic nano-optics lenses,” Appl. Phys. Lett. 85(4), 642–644 (2004).
    [CrossRef]
  4. H. Shi, C. Wang, C. Du, X. Luo, X. Dong, and H. Gao, “Beam manipulating by metallic nano-slits with variant widths,” Opt. Express 13(18), 6815–6820 (2005), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-13-18-6815 .
    [CrossRef] [PubMed]
  5. T. Xu, C. Du, C. Wang, and X. Luo, “Subwavelength imaging by metallic slab lens with nanoslits,” Appl. Phys. Lett. 91(20), 201501 (2007).
    [CrossRef]
  6. T. Xu, C. Wang, C. Du, and X. Luo, “Plasmonic beam deflector,” Opt. Express 16(7), 4753–4759 (2008), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-7-4753 .
    [CrossRef] [PubMed]
  7. L. Verslegers, P. B. Catrysse, Z. Yu, and S. Fan, “Planar metallic nanoscale slit lenses for angle compensation,” Appl. Phys. Lett. 95(7), 071112 (2009).
    [CrossRef]
  8. Y. J. Jung, D. Park, S. Koo, S. Yu, and N. Park, “Metal slit array Fresnel lens for wavelength-scale optical coupling to nanophotonic waveguides,” Opt. Express 17(21), 18852–18857 (2009), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-21-18852 .
    [CrossRef]
  9. L. Verslegers, P. B. Catrysse, Z. Yu, W. Shin, Z. Ruan, and S. Fan, “Phase front design with metallic pillar arrays,” Opt. Lett. 35(6), 844–846 (2010).
    [CrossRef] [PubMed]
  10. L. Verslegers, P. B. Catrysse, Z. Yu, J. S. White, E. S. Barnard, M. L. Brongersma, and S. Fan, “Planar lenses based on nanoscale slit arrays in a metallic film,” Nano Lett. 9(1), 235–238 (2009).
    [CrossRef]
  11. L. Lin, X. M. Goh, L. P. McGuinness, and A. Roberts, “Plasmonic lenses formed by two-dimensional nanometric cross-shaped aperture arrays for Fresnel-region focusing,” Nano Lett. 10(5), 1936–1940 (2010).
    [CrossRef] [PubMed]
  12. W. Srituravanich, N. Fang, C. Sun, Q. Luo, and X. Zhang, “Plasmonic nanolithography,” Nano Lett. 4(6), 1085–1088 (2004).
    [CrossRef]
  13. A. E. Kryukov, Y.-K. Kim, and J. B. Ketterson, “Surface plasmon scanning near-field optical microscopy,” J. Appl. Phys. 82(11), 5411–5415 (1997).
    [CrossRef]
  14. M. Mansuripur, A. R. Zakharian, A. Lesuffleur, S. H. Oh, R. J. Jones, N. C. Lindquist, H. Im, A. Kobyakov, and J. V. Moloney, “Plasmonic nano-structures for optical data storage,” Opt. Express 17(16), 14001–14014 (2009), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-16-14001 .
    [CrossRef] [PubMed]
  15. D. R. Matthews, H. D. Summers, K. Njoh, S. Chappell, R. Errington, and P. Smith, “Optical antenna arrays in the visible range,” Opt. Express 15(6), 3478–3487 (2007), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-15-6-3478 .
    [CrossRef] [PubMed]
  16. Lumerical FDTD Solution, http://www.lumerical.com/
  17. H. C. Kim, H. Ko, and M. Cheng, “High efficient optical focusing of a zone plate composed of metal/dielectric multilayer,” Opt. Express 17(5), 3078–3083 (2009), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-5-3078 .
    [CrossRef] [PubMed]

2010 (2)

L. Verslegers, P. B. Catrysse, Z. Yu, W. Shin, Z. Ruan, and S. Fan, “Phase front design with metallic pillar arrays,” Opt. Lett. 35(6), 844–846 (2010).
[CrossRef] [PubMed]

L. Lin, X. M. Goh, L. P. McGuinness, and A. Roberts, “Plasmonic lenses formed by two-dimensional nanometric cross-shaped aperture arrays for Fresnel-region focusing,” Nano Lett. 10(5), 1936–1940 (2010).
[CrossRef] [PubMed]

2009 (5)

2008 (1)

2007 (2)

2005 (1)

2004 (2)

Z. Sun and H. Kim, “Refractive transmission of light and beam shaping with metallic nano-optics lenses,” Appl. Phys. Lett. 85(4), 642–644 (2004).
[CrossRef]

W. Srituravanich, N. Fang, C. Sun, Q. Luo, and X. Zhang, “Plasmonic nanolithography,” Nano Lett. 4(6), 1085–1088 (2004).
[CrossRef]

2002 (1)

H. J. Lezec, A. Degiron, E. Devaux, R. A. Linke, L. Martin-Moreno, F. J. Garcia-Vidal, and T. W. Ebbesen, “Beaming light from a subwavelength aperture,” Science 297(5582), 820–822 (2002).
[CrossRef] [PubMed]

1998 (1)

T. W. Ebbesen, H. J. Lezec, H. F. Ghaemi, T. Thio, and P. A. Wolff, “Extraordinary optical transmission through sub-wavelength holes arrays,” Nature 391(6668), 667–669 (1998).
[CrossRef]

1997 (1)

A. E. Kryukov, Y.-K. Kim, and J. B. Ketterson, “Surface plasmon scanning near-field optical microscopy,” J. Appl. Phys. 82(11), 5411–5415 (1997).
[CrossRef]

Barnard, E. S.

L. Verslegers, P. B. Catrysse, Z. Yu, J. S. White, E. S. Barnard, M. L. Brongersma, and S. Fan, “Planar lenses based on nanoscale slit arrays in a metallic film,” Nano Lett. 9(1), 235–238 (2009).
[CrossRef]

Brongersma, M. L.

L. Verslegers, P. B. Catrysse, Z. Yu, J. S. White, E. S. Barnard, M. L. Brongersma, and S. Fan, “Planar lenses based on nanoscale slit arrays in a metallic film,” Nano Lett. 9(1), 235–238 (2009).
[CrossRef]

Catrysse, P. B.

L. Verslegers, P. B. Catrysse, Z. Yu, W. Shin, Z. Ruan, and S. Fan, “Phase front design with metallic pillar arrays,” Opt. Lett. 35(6), 844–846 (2010).
[CrossRef] [PubMed]

L. Verslegers, P. B. Catrysse, Z. Yu, J. S. White, E. S. Barnard, M. L. Brongersma, and S. Fan, “Planar lenses based on nanoscale slit arrays in a metallic film,” Nano Lett. 9(1), 235–238 (2009).
[CrossRef]

L. Verslegers, P. B. Catrysse, Z. Yu, and S. Fan, “Planar metallic nanoscale slit lenses for angle compensation,” Appl. Phys. Lett. 95(7), 071112 (2009).
[CrossRef]

Chappell, S.

Cheng, M.

Degiron, A.

H. J. Lezec, A. Degiron, E. Devaux, R. A. Linke, L. Martin-Moreno, F. J. Garcia-Vidal, and T. W. Ebbesen, “Beaming light from a subwavelength aperture,” Science 297(5582), 820–822 (2002).
[CrossRef] [PubMed]

Devaux, E.

H. J. Lezec, A. Degiron, E. Devaux, R. A. Linke, L. Martin-Moreno, F. J. Garcia-Vidal, and T. W. Ebbesen, “Beaming light from a subwavelength aperture,” Science 297(5582), 820–822 (2002).
[CrossRef] [PubMed]

Dong, X.

Du, C.

Ebbesen, T. W.

H. J. Lezec, A. Degiron, E. Devaux, R. A. Linke, L. Martin-Moreno, F. J. Garcia-Vidal, and T. W. Ebbesen, “Beaming light from a subwavelength aperture,” Science 297(5582), 820–822 (2002).
[CrossRef] [PubMed]

T. W. Ebbesen, H. J. Lezec, H. F. Ghaemi, T. Thio, and P. A. Wolff, “Extraordinary optical transmission through sub-wavelength holes arrays,” Nature 391(6668), 667–669 (1998).
[CrossRef]

Errington, R.

Fan, S.

L. Verslegers, P. B. Catrysse, Z. Yu, W. Shin, Z. Ruan, and S. Fan, “Phase front design with metallic pillar arrays,” Opt. Lett. 35(6), 844–846 (2010).
[CrossRef] [PubMed]

L. Verslegers, P. B. Catrysse, Z. Yu, J. S. White, E. S. Barnard, M. L. Brongersma, and S. Fan, “Planar lenses based on nanoscale slit arrays in a metallic film,” Nano Lett. 9(1), 235–238 (2009).
[CrossRef]

L. Verslegers, P. B. Catrysse, Z. Yu, and S. Fan, “Planar metallic nanoscale slit lenses for angle compensation,” Appl. Phys. Lett. 95(7), 071112 (2009).
[CrossRef]

Fang, N.

W. Srituravanich, N. Fang, C. Sun, Q. Luo, and X. Zhang, “Plasmonic nanolithography,” Nano Lett. 4(6), 1085–1088 (2004).
[CrossRef]

Gao, H.

Garcia-Vidal, F. J.

H. J. Lezec, A. Degiron, E. Devaux, R. A. Linke, L. Martin-Moreno, F. J. Garcia-Vidal, and T. W. Ebbesen, “Beaming light from a subwavelength aperture,” Science 297(5582), 820–822 (2002).
[CrossRef] [PubMed]

Ghaemi, H. F.

T. W. Ebbesen, H. J. Lezec, H. F. Ghaemi, T. Thio, and P. A. Wolff, “Extraordinary optical transmission through sub-wavelength holes arrays,” Nature 391(6668), 667–669 (1998).
[CrossRef]

Goh, X. M.

L. Lin, X. M. Goh, L. P. McGuinness, and A. Roberts, “Plasmonic lenses formed by two-dimensional nanometric cross-shaped aperture arrays for Fresnel-region focusing,” Nano Lett. 10(5), 1936–1940 (2010).
[CrossRef] [PubMed]

Im, H.

Jones, R. J.

Jung, Y. J.

Ketterson, J. B.

A. E. Kryukov, Y.-K. Kim, and J. B. Ketterson, “Surface plasmon scanning near-field optical microscopy,” J. Appl. Phys. 82(11), 5411–5415 (1997).
[CrossRef]

Kim, H.

Z. Sun and H. Kim, “Refractive transmission of light and beam shaping with metallic nano-optics lenses,” Appl. Phys. Lett. 85(4), 642–644 (2004).
[CrossRef]

Kim, H. C.

Kim, Y.-K.

A. E. Kryukov, Y.-K. Kim, and J. B. Ketterson, “Surface plasmon scanning near-field optical microscopy,” J. Appl. Phys. 82(11), 5411–5415 (1997).
[CrossRef]

Ko, H.

Kobyakov, A.

Koo, S.

Kryukov, A. E.

A. E. Kryukov, Y.-K. Kim, and J. B. Ketterson, “Surface plasmon scanning near-field optical microscopy,” J. Appl. Phys. 82(11), 5411–5415 (1997).
[CrossRef]

Lesuffleur, A.

Lezec, H. J.

H. J. Lezec, A. Degiron, E. Devaux, R. A. Linke, L. Martin-Moreno, F. J. Garcia-Vidal, and T. W. Ebbesen, “Beaming light from a subwavelength aperture,” Science 297(5582), 820–822 (2002).
[CrossRef] [PubMed]

T. W. Ebbesen, H. J. Lezec, H. F. Ghaemi, T. Thio, and P. A. Wolff, “Extraordinary optical transmission through sub-wavelength holes arrays,” Nature 391(6668), 667–669 (1998).
[CrossRef]

Lin, L.

L. Lin, X. M. Goh, L. P. McGuinness, and A. Roberts, “Plasmonic lenses formed by two-dimensional nanometric cross-shaped aperture arrays for Fresnel-region focusing,” Nano Lett. 10(5), 1936–1940 (2010).
[CrossRef] [PubMed]

Lindquist, N. C.

Linke, R. A.

H. J. Lezec, A. Degiron, E. Devaux, R. A. Linke, L. Martin-Moreno, F. J. Garcia-Vidal, and T. W. Ebbesen, “Beaming light from a subwavelength aperture,” Science 297(5582), 820–822 (2002).
[CrossRef] [PubMed]

Luo, Q.

W. Srituravanich, N. Fang, C. Sun, Q. Luo, and X. Zhang, “Plasmonic nanolithography,” Nano Lett. 4(6), 1085–1088 (2004).
[CrossRef]

Luo, X.

Mansuripur, M.

Martin-Moreno, L.

H. J. Lezec, A. Degiron, E. Devaux, R. A. Linke, L. Martin-Moreno, F. J. Garcia-Vidal, and T. W. Ebbesen, “Beaming light from a subwavelength aperture,” Science 297(5582), 820–822 (2002).
[CrossRef] [PubMed]

Matthews, D. R.

McGuinness, L. P.

L. Lin, X. M. Goh, L. P. McGuinness, and A. Roberts, “Plasmonic lenses formed by two-dimensional nanometric cross-shaped aperture arrays for Fresnel-region focusing,” Nano Lett. 10(5), 1936–1940 (2010).
[CrossRef] [PubMed]

Moloney, J. V.

Njoh, K.

Oh, S. H.

Park, D.

Park, N.

Roberts, A.

L. Lin, X. M. Goh, L. P. McGuinness, and A. Roberts, “Plasmonic lenses formed by two-dimensional nanometric cross-shaped aperture arrays for Fresnel-region focusing,” Nano Lett. 10(5), 1936–1940 (2010).
[CrossRef] [PubMed]

Ruan, Z.

Shi, H.

Shin, W.

Smith, P.

Srituravanich, W.

W. Srituravanich, N. Fang, C. Sun, Q. Luo, and X. Zhang, “Plasmonic nanolithography,” Nano Lett. 4(6), 1085–1088 (2004).
[CrossRef]

Summers, H. D.

Sun, C.

W. Srituravanich, N. Fang, C. Sun, Q. Luo, and X. Zhang, “Plasmonic nanolithography,” Nano Lett. 4(6), 1085–1088 (2004).
[CrossRef]

Sun, Z.

Z. Sun and H. Kim, “Refractive transmission of light and beam shaping with metallic nano-optics lenses,” Appl. Phys. Lett. 85(4), 642–644 (2004).
[CrossRef]

Thio, T.

T. W. Ebbesen, H. J. Lezec, H. F. Ghaemi, T. Thio, and P. A. Wolff, “Extraordinary optical transmission through sub-wavelength holes arrays,” Nature 391(6668), 667–669 (1998).
[CrossRef]

Verslegers, L.

L. Verslegers, P. B. Catrysse, Z. Yu, W. Shin, Z. Ruan, and S. Fan, “Phase front design with metallic pillar arrays,” Opt. Lett. 35(6), 844–846 (2010).
[CrossRef] [PubMed]

L. Verslegers, P. B. Catrysse, Z. Yu, and S. Fan, “Planar metallic nanoscale slit lenses for angle compensation,” Appl. Phys. Lett. 95(7), 071112 (2009).
[CrossRef]

L. Verslegers, P. B. Catrysse, Z. Yu, J. S. White, E. S. Barnard, M. L. Brongersma, and S. Fan, “Planar lenses based on nanoscale slit arrays in a metallic film,” Nano Lett. 9(1), 235–238 (2009).
[CrossRef]

Wang, C.

White, J. S.

L. Verslegers, P. B. Catrysse, Z. Yu, J. S. White, E. S. Barnard, M. L. Brongersma, and S. Fan, “Planar lenses based on nanoscale slit arrays in a metallic film,” Nano Lett. 9(1), 235–238 (2009).
[CrossRef]

Wolff, P. A.

T. W. Ebbesen, H. J. Lezec, H. F. Ghaemi, T. Thio, and P. A. Wolff, “Extraordinary optical transmission through sub-wavelength holes arrays,” Nature 391(6668), 667–669 (1998).
[CrossRef]

Xu, T.

T. Xu, C. Wang, C. Du, and X. Luo, “Plasmonic beam deflector,” Opt. Express 16(7), 4753–4759 (2008), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-7-4753 .
[CrossRef] [PubMed]

T. Xu, C. Du, C. Wang, and X. Luo, “Subwavelength imaging by metallic slab lens with nanoslits,” Appl. Phys. Lett. 91(20), 201501 (2007).
[CrossRef]

Yu, S.

Yu, Z.

L. Verslegers, P. B. Catrysse, Z. Yu, W. Shin, Z. Ruan, and S. Fan, “Phase front design with metallic pillar arrays,” Opt. Lett. 35(6), 844–846 (2010).
[CrossRef] [PubMed]

L. Verslegers, P. B. Catrysse, Z. Yu, J. S. White, E. S. Barnard, M. L. Brongersma, and S. Fan, “Planar lenses based on nanoscale slit arrays in a metallic film,” Nano Lett. 9(1), 235–238 (2009).
[CrossRef]

L. Verslegers, P. B. Catrysse, Z. Yu, and S. Fan, “Planar metallic nanoscale slit lenses for angle compensation,” Appl. Phys. Lett. 95(7), 071112 (2009).
[CrossRef]

Zakharian, A. R.

Zhang, X.

W. Srituravanich, N. Fang, C. Sun, Q. Luo, and X. Zhang, “Plasmonic nanolithography,” Nano Lett. 4(6), 1085–1088 (2004).
[CrossRef]

Appl. Phys. Lett. (3)

Z. Sun and H. Kim, “Refractive transmission of light and beam shaping with metallic nano-optics lenses,” Appl. Phys. Lett. 85(4), 642–644 (2004).
[CrossRef]

T. Xu, C. Du, C. Wang, and X. Luo, “Subwavelength imaging by metallic slab lens with nanoslits,” Appl. Phys. Lett. 91(20), 201501 (2007).
[CrossRef]

L. Verslegers, P. B. Catrysse, Z. Yu, and S. Fan, “Planar metallic nanoscale slit lenses for angle compensation,” Appl. Phys. Lett. 95(7), 071112 (2009).
[CrossRef]

J. Appl. Phys. (1)

A. E. Kryukov, Y.-K. Kim, and J. B. Ketterson, “Surface plasmon scanning near-field optical microscopy,” J. Appl. Phys. 82(11), 5411–5415 (1997).
[CrossRef]

Nano Lett. (3)

L. Verslegers, P. B. Catrysse, Z. Yu, J. S. White, E. S. Barnard, M. L. Brongersma, and S. Fan, “Planar lenses based on nanoscale slit arrays in a metallic film,” Nano Lett. 9(1), 235–238 (2009).
[CrossRef]

L. Lin, X. M. Goh, L. P. McGuinness, and A. Roberts, “Plasmonic lenses formed by two-dimensional nanometric cross-shaped aperture arrays for Fresnel-region focusing,” Nano Lett. 10(5), 1936–1940 (2010).
[CrossRef] [PubMed]

W. Srituravanich, N. Fang, C. Sun, Q. Luo, and X. Zhang, “Plasmonic nanolithography,” Nano Lett. 4(6), 1085–1088 (2004).
[CrossRef]

Nature (1)

T. W. Ebbesen, H. J. Lezec, H. F. Ghaemi, T. Thio, and P. A. Wolff, “Extraordinary optical transmission through sub-wavelength holes arrays,” Nature 391(6668), 667–669 (1998).
[CrossRef]

Opt. Express (6)

H. Shi, C. Wang, C. Du, X. Luo, X. Dong, and H. Gao, “Beam manipulating by metallic nano-slits with variant widths,” Opt. Express 13(18), 6815–6820 (2005), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-13-18-6815 .
[CrossRef] [PubMed]

Y. J. Jung, D. Park, S. Koo, S. Yu, and N. Park, “Metal slit array Fresnel lens for wavelength-scale optical coupling to nanophotonic waveguides,” Opt. Express 17(21), 18852–18857 (2009), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-21-18852 .
[CrossRef]

T. Xu, C. Wang, C. Du, and X. Luo, “Plasmonic beam deflector,” Opt. Express 16(7), 4753–4759 (2008), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-16-7-4753 .
[CrossRef] [PubMed]

H. C. Kim, H. Ko, and M. Cheng, “High efficient optical focusing of a zone plate composed of metal/dielectric multilayer,” Opt. Express 17(5), 3078–3083 (2009), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-5-3078 .
[CrossRef] [PubMed]

M. Mansuripur, A. R. Zakharian, A. Lesuffleur, S. H. Oh, R. J. Jones, N. C. Lindquist, H. Im, A. Kobyakov, and J. V. Moloney, “Plasmonic nano-structures for optical data storage,” Opt. Express 17(16), 14001–14014 (2009), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-17-16-14001 .
[CrossRef] [PubMed]

D. R. Matthews, H. D. Summers, K. Njoh, S. Chappell, R. Errington, and P. Smith, “Optical antenna arrays in the visible range,” Opt. Express 15(6), 3478–3487 (2007), http://www.opticsinfobase.org/oe/abstract.cfm?URI=oe-15-6-3478 .
[CrossRef] [PubMed]

Opt. Lett. (1)

Science (1)

H. J. Lezec, A. Degiron, E. Devaux, R. A. Linke, L. Martin-Moreno, F. J. Garcia-Vidal, and T. W. Ebbesen, “Beaming light from a subwavelength aperture,” Science 297(5582), 820–822 (2002).
[CrossRef] [PubMed]

Other (1)

Lumerical FDTD Solution, http://www.lumerical.com/

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Figures (5)

Fig. 1
Fig. 1

Scanning electron micrographs of plasmonic lenses in an aluminium film. (a) and (b) are lenses designed to have f = 3 µm and f = 6 µm, respectively. (c) An enlarged image of the region inside the solid black rectangle in (a).

Fig. 2
Fig. 2

(a) Focusing light pattern in the xz plane obtained by the CSOM for a lens designed to have f = 3 μm and (b) for a lens designed to have f = 6 μm. The horizontal white line in (a) and (b) shows the position of the sample surface. (c) Simulation results for the f = 3 μm lens and (d) simulation results for the f = 6 μm lens.

Fig. 3
Fig. 3

(a) Normalized simulation and experimental results for the light intensity distributions of the lenses. The optical axis is at x = 0 and the lens plane is at z = 0. (a) and (b) show the distribution along the z direction through the foci of the lenses with f = 3.1 µm and f = 6.1 µm respectively. (c) and (d) show the distribution along the x-direction through the foci of the lenses with f = 3.1 µm and f = 6.1 µm respectively.

Fig. 4
Fig. 4

(a)-(c) Focusing light pattern in the xz plane obtained by the CSOM for the lenses written using electron beam lithography with doses of (1-25%)D 0, (1-10%)D 0 and (1 + 10%)D 0, respectively, where D 0 = 550 µC/cm2. All lenses have the same design as the lens in Fig. 2(b). The horizontal white line shows the position of the sample surface.

Fig. 5
Fig. 5

Measured light intensity distributions along, (a) z, and (b) x directions through the foci of the devices written by electron beam lithography at different doses, respectively. The designed f is 6 µm. The central slit locates at x = 0 and the sample surface is at z = 0.

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